Soleplate for irons and method for making the same



l Oct. 10, 1950 R. L. ITRIMBLE SOLEPLATE FOR IRONS AND METHOD FOR MAKING THE SAME 2 Sheets-Sheet 1 Filed NOV. 14, 1947- INVENTOR. F 4, TrlMi/e. BY

F770 FIVEL Oct. 10, 1950 R. L. TRIMBLE 2,524,944

souazm'rs FOR IRONS AND METHOD FOR MAKING ms SAME Filed Nov. 14, 1947 2 Sheets-Sheet 2 INVENTOR. 77a; ,4, TriwZZ-r.

BYgJW Patented Oct. 10, 1950 SOLEPLATE FOR IRONS AND METHOD-FOR MAKING THE SAME Roy L. Trimble, Bloomington, Ill., assignor to Eureka Williams Corporation, Bloomington, 111.,

a corporation of Michigan Application November 14, 1947, Serial No. 785,870

6 Claims.

This invention relates to electrical heating plates or units such as sometimes are employed as sole plates for irons, grid'surfaces for wafiie irons, heating elements for electric stoves, etc. The invention also comprises a novel method and an apparatus for manufacturing such plates, grids or elements.

Some of the objects of the invention are:

To provide an electrically insulated electrical resistance element which can be manufactured at relatively low cost, which will have substantially an equal rate of heat transfer in all directions radially outwardly with respect to the electrical resistance wire or member, and which electrically insulated element or unit may be cast or otherwise embedded in a fluid metal body, the extraction of the heat of fusion from which will place the insulating material of the unit under compression so as to provide the best possible thermal contact relation between the resistance element and the body. 7

Other and further objects of the invention will be apparent from the following description'and claims and will be understood by reference to the accompanying drawings, of which there are two sheets, which, by way of illustration, show a preferred embodiment and the principles thereof and what I now consider to be the best mode in which I have contemplated applying those principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes maybe made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims. I also contemplate that of the several different features of my invention, certain ones thereof may be advantageously employed in some applications separate and apart from the remainder of the features.

Referring to the drawings:

Figures 1, 2, 3, 4 and 5 disclose sections of a mold in which an electrical resistance element embracing the principles of the invention is being progressively formed.

Figure 6 is a fragment of the mold in the position shown by Figure 1 except that Figure 6 illustrates a section through a different part of the resistance element being formed.

Figure 7 illustrates a cross-sectional view through a section'of the heat insulating sheath, after the formation of the section has been completed and before the resistance member is disposed therein.

Figure 8 is a cross-sectional view through a completed insulated resistance element as the same might appear in a vertical plane through one of the terminals at the end of the unit.

Figure 9 is a view similar to that shown by Figure 8 except that Figure 9 is taken on averticalplane remote from the terminal ends of the unit.

Figure 10 is a plane view of the completed electrical resistance unit or element.

Figure 11 is an end elevation view of the struc ture shown in Figure 10.

Figure 12 is a view of a mold in which the unit illustrated, by Figures 10 and 11 is supported in position for casting the same in molten or fluid metal to be poured into the mold.

Figure 13 is a plane view of the sole plate of an iron in which the invention is employed.

Figure 14 is a cross-sectional view through the structure shown by Figure 13, taken substantially in the plane of line I 4! 4 thereon looking in the direction of the arrows.

Referring particularly to Figures 10 and 11, the numeral It! indicates generally an electrically insulated resistance heating element or unit embracing the principles of the invention. In the embodiment of the invention shown by Figures 10 and 11 the unit [0 is formed in somewhat the shape of the sole plate of an iron except that the element I0 is somewhat smaller than the sole plate of an iron due to the fact that it is desirable to space the element within the sole plate structure in such a way that the unit will be located somewhat inwardly of the outer edges of the sole plate. The ends of the element [0 adapted to be disposed near the rear or unpainted end of the sole plate are turned inwardly as indicated at II and these are provided with upwardly projecting electrically insulated terminal blocks l2 and 13 from which the ends of the resistance wire l4 project. The pointed or front end of the element has an upwardly projecting support l6 for purposes to be hereinafter described. The unit In consists of a metallic armor or support 11, an electrically insulating sheath [8 and an electrical resistance member or wire l9 (see also Figures 1 to 9).

In forming the unit 10 there is employed a mold 2| having a channel 22 formed therein, the configuration of which is comparable to the plan view of the electrical resistance unit to be formed. In the present instance the plan view of the channel 22 will be the same as the plan view of the resistance unit lfl'illustrated by Figure 10. The mold 2| comprises a lower movable part 23 which is disposed within the channel or cavity 22 for the purpose of supporting and. measuring within .ing surface of the armor l7.

the cavity 22 the amount of electrical resistance material 26 required for making the upper section of the sheath l8. The upper section when completed is indicated by the numeral 24 in Figure 7. When the lower movable part 23 is held in the mold 2! in the position illustrated by Figure 1 the amount of loose insulating material which will exactly fill the mold to the top of the cavity 22 is the right amount for making the section 24 of the sheath l8.

In Figure 1 the lower movable part 23 of the mold 2| has an arcuate upper surface on which the arcuate armor H is positioned before the insulating material 26 is disposed and measured within the cavity 22. Flanges 28 formed at opposite ends of the armor l! are adapted to receive the insulating terminals l2. Also the support I6 is secured in a flanged depression formed in the front or pointed part of the armor IT. The mold section 22 is of course recessed to fit and to support the terminals l2 and the support l6. Small openings indicated at 23 extend vertically through the terminal blocks I2 and communicate with clearance spaces 3| directly beneath the central portions of the terminals l2.

In order to compress the insulating material 26 upon the armor H a downwardly movable part or plunger 32 is employed (see Figure 2). The plunger 32 is shaped to conform to the configuration of the channel or cavity 22 and is provided at its lower end with an arcuate bead or projection indicated at 33 which is relatively concentric to the configuration of the insulating material support- Outwardly from each edge of the arcuate surface 33 are aligned planular surfaces 34 which are adapted to define a parting line between the lower and upper sections of the insulating sheath l8. Opposite the terminal blocks [2 the plunger 32 is provided with downwardly projecting punches 36 which are disposed in alignment with the openings 3| and which are adapted to form in the insulating material 26 openings for the resistance wire in alignment with the openings 3|.

When the plunger 32 is applied to the insulating material as is illustrated in Figure 2 the lower movable part 23 of the mold 2| is moved downwardly against shoulders 31 adapted to support the part 23 in such a way as to receive the force applied by the plunger 32. The insulating material 26 is progressively compressed and compacted by the application of the plunger 32 until the thickness of the compressed and compacted insulating material is substantially equal in all directions between the arcuate surface 33 of the plunger 32, the supporting surface of the armor l"! and the sides of the cavity 22. When the plunger 32 is removed the insulating material 26 will remain compacted upon the armor H in such a manner that an arcuate channel or groove 38 will be formed in the upper part of the sheath section 24 by the head 33 projecting from the lower surface of the plunger 32.

Figure 3 illustrates the next step in the process of forming the unit In in which a spirally wound electrical resistance element 4| is disposed within the groove or channel 38. The resistance element 4| is formed in such a manner as to have a curvature change greater than the curvature of the channel 38. In the instance illustrated by Figure 3 the element or wire 4| is spirally wound in such manner as to provide convolutions which appear as circles in cross-section, the radii of such circles being less than the radius of curvature of the channel or groove 38. The opposite ends of the element or wire 4| are bent laterally in such a way as to extend through the terminal openings 29 and into the clearance space 3| beneath to provide the terminal wires l4, previously referred to. In order to measure the cor rect quantity of electrical insulating material. 26 the lower movable part 23 is moved upwardly away from the supporting shoulders 31 into the position illustrated by Figure 3. Thereafter the cavity 22 is filled with the insulating material 26, such material being placed in the cavity 22 on top of the sheath section 24 and the spirally wound wire 4|. The wire 4| is wound in such a manner that the convolutions thereof are separated far enough so that the insulating material 26 will fill the spaces within and between the convolutions of the wire 4|.

Figure 4 illustrates the manner in which the insulating material 26 is compressed and compacted upon the previously formed section 24 of the sheath IE to form a complete and integral unit of the sheath l8, the electrical resistance wire 4| and the armor H.

To perform this step in the process there is employed a second plunger 42 similar to the plunger 32 except that the lower surface thereof employed in compressing and compacting the insulating material 26 is formed with a curvature similar to the curvature of the upper surface of the lower movable part 23 exc -t opposite in relation thereto. When the plunger 12 is brought downwardly in the mold 2% the insulating material 26 is progressively coinpr Bed and compacted upon the sheath section 2 3 the insulating material is also compressed a compacted upon the spirally wound wire The force of compressing and compacting t insulating material upon the wire :li tends flatten each convolution of the wire, such co pressing and compacting being continued until the wire 4| takes the shape indicated at l3 in Figure 8, in which oppositely disposed portions 43 and 44 of each convolution of the wire have approximately the same curvature as the channel 38. When the wire 4| has been compressed to this extent the thickness of the compacted insulating material surrounding the wire will be approximately equal in all directions normally with respect to each convolution of the wire.

After the unit l8 has been formed in this manner the plunger 42 is removed and. the lower movable part 23 of the mold 2| is elevated as indicated in Figure 5 so that the composite and. unitary element 10 can be removed from the mold.

After the unit l0 has been removed the unit may be embedded in fluid metal as, for example, in the casting process illustrated by El we 12.

ly movable parts 41 and 48 formed of a: v able material and between which is pro mold cavity 49 having a configuration co able to any element which it is desired to l,

any desired kind may be poured into the 49. In the structure shown by Figures and 14 the cavity 48 is in the form of plate of an iron, the upper surface 52 of the ity being in the form of a planular o roughly approximately the working or ironing surface of an iron, the lower surface 53 of the cavity corresponding to the upper surface of the plate.

sole plate, while the side surfaces 54 of the cavity correspond to the side surfaces of the sole It will be noted from Figure 12 that the unit In is disposed in the cavity 49 in such manner as to be supported by the support it which is formed as a part of the armor ll and by the two terminal blocks [2. The support l6 and terminal blocks [2 are disposed in openings formed in the part 41 of the mold '45 in such a manner that the support and terminals are held high enough within the cavity 49 that the armor I1 and flanges formed thereon around the support l5 and the terminals l2 do not engage the surface of the mold. Under such circumstances it will be apparent that when the cavit 49 is filled with molten metal the entire unit In, in cluding the armor I! will be entirely embedded within the molten metal with only the support l6 and terminals l2 projecting therefrom.

After the molten metal is poured into the cavity 49 the entire mold is allowed to cool until such time as the parts 41 and 48 of the mold 46 can be separated and the finished casting indicated at 56 removed from the mold sections. Thereafter the metal of the casting 56 will continue to cool until the same is approximately at room temperature. During the entire process of cooling, the metal of which the casting 56 is formed will contract upon the unit If and will continue to further compress compact the various elements of the unit IQ into a more composite unit and one in which the exterior surface of the sheath l8 will be brought into direct and intimate thermal contact with the metallic surface of the body of metal comprising the cast ing 56 and the interior surface of the armor it. By observing Figure 14 it will be noted that the'thickness of the sheath I8 is substantially equal in all directions from the resistance wire I9 embedded therein, that the sheath i8 is in intimate thermal contact with the metallic body forming the casting 55 throughout a major portion of the exterior surface thereof and that such surface is adjacent the surface 52 which in the present instance is the working or ironing surface of the sole plate of an iron. Under such circumstances it will be apparent that the heat transfer rate from the resistance wire E9 will be substantially equal in all directions and particu larly toward the ironing surface 52 and in which direction it is desired that heat shall be conducted in all directions at substantially a. uniform rate.

Since heat will be conducted in all directions from the resistance wire L! at a substantially uniform rate it will be apparent that no hot spots will develop in any portion of any convolutions of the wire l9 and consequently the wire [9 will not burn out readily.

The armor or shield ll, it will be noted from Figure 14, is disposed away from the ironing surface 52 and in which direction it is not desired to conduct heat at the maximum rate. Howeverthe shield or armor l1 will absorb heat from the wire l9 at substantially the same rate as the metallic casting surrounding the remainder of the sheath l8 and will conduct this heat transversely of the sheath in such a way that a considerable part of this heat will be delivered to the cast material on opposite sides of the unit and from whence the heat will be conducted by the cast body to the sole plate where it is desired to employ the heat.

While I have illustrated and described a preferred embodiment of my invention, it is understood that this is capable of modification, and I therefore do not wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall within the purview of the following claims.

I claim: I

l. A heating plate comprising a fused metallic body having electrical insulating terminals projecting therefrom, an electrical resistance heat ing element within said body and extending through and between said terminals, said heating element comprising a wire, a compressed sheath of dielectric material surrounding said wire and disposed between said wire and said body, the cross-sectional outline of said sheath being substantially oval shaped, said sheath being held under compression by said body in intimate thermal contact with said body and being substantially equal in thickness in all directions normally with respect to said wire between the longitudinal axis of said wire and the heating surface of said plate, and. an arcuate shield secured to said sheath and in intimate thermal contact with said sheath and said body, said shield being positioned on the side of said sheath remote from said heating surface and having openings therein through which said terminals project. I

2. A heating plate comprising a fused metallic body having a heating surface formed thereon, and an elongated electrical resistance heating element the cross-sectional outline Of which is substantially oval shaped, cast within said body,

said heating element comprising a spirally wound wire electrically insulated from said body, the electrical insulating material about said wire being of approximately equal thickness normally with respect to the convolutions of said wire,

and an arcuate shield secured to said heating element along the surface thereof remote from said heating surface of said body.

3. A sole plate for irons comprising a fusedmetallic body having an ironing surface formed thereon, and an electrical resistance heating element cast within said body, said heating element comprising a spirally wound wire electricallyinsulated from said body, the convolutions of said wire having major and minor axes, said major axes being parallel to said ironing surface, and an arcuate shield secured to the insulating material about said wire along the surface thereof remote from said ironing surface, said insulating material and said shield being in intimate thermal contact with said body in all directions radially outwardly of said convolutions and between the longitudinal axis of said wire and said ironing surface.

4. A method of forming heating plates which comprises forming an electrical resistance heating wire to provide a heating unit having convolutions, compressing a segment of an electrical insulating sheath for said unit upon an elongated arcuate shield, forming a longitudinally extending groove in said segment, the radius of curvature of said groove being greater than the radius of curvature of said convolutions, disposing another segment of said electrical insulating sheath upon said first segment and said heating unit, compressing and compacting said unit in said groove and said other segment upon said unit and said first segment for completing said sheath about said heating unit, said compressing and compacting operation being continued until the radius of curvature of said convolutions of said unit approximates the radius of curvature of said groove, embedding said sheath in fluid metal with said sheath directly engaging said fluid metal, and then extracting from said metal the heat of fusion of said metal for further compressing and compacting said insulating material upon said unit and in engagement With said metal during the contraction of said metal resulting from said extraction.

5. A method of forming sole plates for irons which comprises spirally forming an electrical resistance heating wire to provide a heating unit having convolutions of uniform radius of curvature, compressing a segment of an electrical insulating sheath for said unit upon an elongated arcuate shield, forming a groove in said segment, the radius of curvature of said groove being greater than the radius of curvature of said convolutions, disposing another segment of said electrical insulating sheath upon said first segment and said heating unit by compressing and compacting said unit in said groove and said other segment upon said unit and said first segment for completing said sheath about said heating unit, said compressing and compacting opera tion being continued until the radius of curvature of said convolutions of said unit approximates the radius of curvature of said groove and until said sheath is approximately equal in thickness in all directions normally with respect to the curvature of said unit, embedding said sheath in fluid metal with said sheath directly engaging said fluid metal, and then extracting from said metal the heat of fusion of said metal for further compressing and compacting said insulating material upon said unit and in engagement with said metal during the contraction of said metal resulting from said extraction.

6. A method of forming sole plates for irons which comprises spirally forming an electrical resistance heating Wire to provide a heating unit having convolutions of uniform radius of curvature, compressing a segment of an electrical insulating sheath for said unit upon an elongated arcuate shield, forming a groove longitudinally.

in said segment, the radius of curvature of said groove being greater than the radius of curvature of said unit, disposing said heating unit longitudinally in said groove, disposing upon said first segment and said heating unit another segment of electrical insulating material forming said sheath, compressing and compacting said other segment thereon for completing said sheath about said heating unit, said compressing and compacting being continued until the radius of curvature of said convolutions of said unit approximates the radius of curvature of said groove, embedding said sheath in fluid metal with said sheath directly engaging said fluid metal and With the major axis of said heating unit in parallel relation to a planular surface, and then eXtracting from said metal the heat of fusion of said metal for further compressing and compacting said insulating material upon said unit and in engagement with said metal during the contraction of said metal resulting from said extraction.

ROY L. TRIMBLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,222,192 Arnold et al Nov. 19, 1940 2,259,242 Clark Oct. 14, 1941 2,331,093 Holand Oct. 5, 1943 2,389,587 Appleman Nov. 27, 1945 2,389,588 Woodman Nov. 27, 1945 2,403,022 Reimers July 2, 1946 2,428,900 Wiegand Oct. 14, 1947 2,458,471 Hammel et al. Jan. 4, 1949 

